The objective of the proposed research is to obtain information on the function of the intestine and the intestinal bacteria through study of the absorption and excretion of intestinal gases. Specifically, four general types of studies will be carried out. 1) Measurements of inert gas absorption will be employed to study the mucosal circulation of the intestine in man and animals. 2) Measurements of breath H2 excretion will be employed to study carbohydrate malabsorption and small bowel transit time in man. 3) An intestinal washout technique employing a constant infusion of argon will be employed to study the volume, composition, source and transit time of intestinal gas in man. 4) Volatile substances produced by the intestinal bacteria will be identified in expired air using gas chromatography-mass spectroscopy. The bacteria that produce these gases will be identified and the factors regulating the metabolism of these bacteria will be investigated.